1. Field of the Invention
The present invention relates generally to storage device controllers, and more particularly, to reading and writing data using a buffer controller.
2. Background
Conventional computer systems typically include several functional components. These components may include a central processing unit (CPU), main memory, input/output (“I/O”) devices, and streaming storage devices (for example, tape drives) (referred to herein as “storage device”). In conventional systems, the main memory is coupled to the CPU via a system bus or a local memory bus. The main memory is used to provide the CPU access to data and/or program information that is stored in main memory at execution time. Typically, the main memory is composed of random access memory (RAM) circuits. A computer system with the CPU and main memory is often referred to as a host system.
The storage device is coupled to the host system via a controller that handles complex details of interfacing the storage devices to the host system. Communications between the host system and the controller is usually provided using one of a variety of standard I/O bus interfaces.
Typically, when data is read from a storage device, a host system sends a read command to the controller, which stores the read command into the buffer memory. Data is read from the device and stored in the buffer memory.
Previously data from a storage device was sent to the controller in 8-bit sizes (i.e. byte oriented where 1 byte is equal to 8 bits) and the controllers were designed to operate with 8-bit format. However, changes by some storage device manufacturers, for example, hard disk manufacturers, will now provide data in 10-bit format (i.e., symbol oriented where one symbol is equal to 10 bits). Other storage device manufacturers, for example, tape drives manufacturers, will continue to provide data in 8-bit format. Due to the disparity in data formats, conventional controllers fail to efficiently handle 8-bit to 10 bits and 10 bit to 8 bit conversion.
Therefore, there is a need for a controller that can efficiently handle data transfer where data may enter the controller in more than one format.